Synthesis, characterization, and biological investigation of new mixed-ligand complexes

A novel series of mixed-ligand complexes of 5,5 '-{(1E,1E ')-1,4-phenelynebis(diazene-2,1-diyl)}bis(quinolin-8-ol) (H2L1) as a primary ligand and 4-aminoantipyrine(L-2) as a secondary ligand with Mn(II) ion were prepared using two general formulae: [Mn-2(H2L1)(2)(L-2)(2)X-4].4Cl (X = OH2(1), ONO2-(2), Cl=nil; OAc(3), Cl = nil) and [Mn-2(H2L1)(L-2)(2)(O2SO2)(2)](4). Free ligands and their complexes were characterized. Electronic absorption spectra of the mixed-ligand complexes indicate a distorted octahedral geometry around the central metal ion, and the anions X- are in the axial positions for all compounds. The ligands behave in a neutral bidentate manner, through nitrogen atoms and oxygen atoms of the carbonyl group (L-2), whereas H2L1 coordinated through nitrogen and OH groups as a neutral bidentate ligand. All complexes do not contain coordinated water molecules, but complex (1) contains four water molecules. The water molecules are removed in a single step. The complexes exhibited magnetic susceptibility corresponding to five unpaired electrons. The antimicrobial activity of the Mn(II) mixed-ligand complexes (1-4) against two gram-positive bacteria, three local gram-negative bacteria, and three fungi species was tested. Mn(II) mixed-ligand complex (2) exhibited significant antibacterial activity against Bacillus cereus, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas sp. Mixed-ligand complex (2) exhibited a high potential cytotoxicity against the growth of human lung cancer cells.